1. Field of the Invention.
This invention relates to pouch containers and, more particularly, to pouch containers for protecting during transport electronic components which are sensitive to electrostatic influences.
2. Description of the Prior Art
Containers for transporting electrostatic-sensitive electronic components have severe design constraints imposed thereon. In particular, various electronic components such as metal oxide semiconductors (MOS), thick and thin film deposited products and other similar devices are highly sensitive to accumulations and discharging of electric charge, an excess accumulation of which may severely damage the device. Precautions typically taken to minimize static electric discharges through the devices during shipment include the use of shorting bars to ground the leads of the device. Also, some devices or components are manufactured with built-in zener diodes to provide protection from low-energy sources.
Although the foregoing techniques are normally adequate to protect the transported components from harmful electrostatic influences, it is sometimes necessary to provide yet additional protection. Such additional protection frequently takes the form of a shipping enclosure commonly referred to as a Faraday cage. A Faraday cage may be defined as a system of conductors forming an essentially continuous conducting mesh or network about the object protected and may include conductors necessary for interconnection between the object protected and an adequate ground. A typical prior art Faraday cage-type shipping enclosure has taken the form of an injection molded plastic container formed around a wire mesh screen in which the wire mesh screen forms an equipotential surface protecting the enclosed device from external electrostatic influences. In addition, the conductors forming the equipotential surface serve to dissipate any accumulation of electric charge built up on the enclosed devices by providing a conductive path between the devices and a source of ground potential.
The shipping container disclosed in U.S. Pat. No. 4,241,829 of Hardy provides a Faraday cage-type enclosure designed to protect the enclosed components from damage resulting from physically disturbing or stressing the container. The container comprises a box-like structure having a bottom, a pair of opposed side walls, a pair of opposed end walls and a top movable between an open and a closed position. A conductive coating is formed overlying substantially the entire interior and exterior surfaces of the box-like structure and includes a portion extending continuously therebetween. A liner of convoluted foam impregnated with a conductive material is secured to the interior surfaces of the top and bottom of the container, the impregnated conductive material forming a continuous conductive path with the conductive coating. The container then forms a Faraday cage-type enclosure providing increased protection from electrostatic influences by establishing a conductive shield of extremely high integrity, the convoluted foam liners promoting intimate contact between the conductive shield and the protected components.
German Offenlegungsschrift No. 2821182 discloses a packaging bag for electronic components that could be damaged by electrostatic charge. The bag comprises a single electrically conductive plastic film and a single transparent piece of plastic film, the films being edge welded together.
U.S. Pat. No. 3,768,724 of Hill discloses a cushioned shipping bag for protecting articles, including electronic components, during shipment. The bag includes two outer bag walls made of a material which is readily heat sealed, two layers of cushioning material and, in one embodiment, two additional inner bag walls. A Faraday cage is not provided.
U.S. Pat. No. 4,247,002 of Horian discloses an envelope for storing phonograph records, the envelope being made from extruded plastic film having an anti-static agent extruded within the film. The envelope has a closed end and sides, the open end and the plastic layers have cooperable projections that are snapped into engagement with each other to provide a seal for the envelope.
Although the aforementioned references disclose various techniques for transporting articles, including electronic components, which protect the article during transport from damage due to electrostatic charge and physical causes, there is still a need for a flexible, pouch-like container having a Faraday cage with a simplified construction which is particularly useful for protecting a sensitive electronic device during production line assembly work on the device.